This invention relates to a system or apparatus for and to a method of electrically interconnecting a multiplicity of lighting fixtures (or other electrical appliances) using three-phase alternating current (AC) power and using five conductors, that is, one conductor for each phase, a ground conductor, and a neutral conductor.
In recent years, modern office and other commercial buildings have become common which utilize a suspended ceiling having a grid or matrix framework suspended from the overhead ceiling/floor structure of the building with the grid framework supporting removable ceiling panels. The grid framework is typically constructed so that at desired locations, one or more of the ceiling panels may be omitted and a fluorescent lighting fixture may be fitted into the framework in place of the ceiling panels. For example, the grid framework may form two foot (60.9 cm.) squares for receiving the removable ceiling panels. A typical lighting fixture may be two feet by four feet and the lighting fixtures may be arranged in the ceiling framework in rows with one or two ceiling panels between the ends of adjacent lighting fixtures of the same row and with one or two ceiling panels between each row of the lighting fixture.
Oftentimes, in a new office building, it is conventional to install the ceiling panels and lighting fixtures before any interior partitions forming the suites of offices have been erected. Then, when the building is leased or when the desired floor plan is chosen, interior partitions are then erected by securing the partitions to the floor. Oftentimes, the partitions are not secured to the suspended ceiling. In the past, the lighting fixtures were "hardwired" by electricians requiring considerable skill and labor. For example, the lighting fixtures for one suite of offices would be connected on one or more separate control switches and the lighting fixtures for an adjacent suite of offices would be connected on a separate control switch. If it became necessary to rewire the lighting fixtures, because, for example, of a change in floor plan, it would be necessary for an electrician to rewire the lighting fixtures.
Recognizing these problems, various plug/in electrical wiring systems became commercially available. One such system is shown in U.S. Pat. No. 4,001,571 to Martin. While the system shown in Martin worked well for its intended purpose, this system utilized single phase AC electrical power and required the crossing of the two leads so as to switch the connection of the lamps from one circuit to the other through the use of so-called converter adapters. This required the use of stacked plug/in connectors, and in certain instances, up to five such connectors must be stacked. Thus, a great many electrical parts were required for utilizing this system and the possibility of poor electrical connections within the stacked connectors was increased.
In the inventor's coassigned U.S. Pat. No. 4,134,045, many of the problems with prior electrical interconnect systems were overcome by employing convenient, interchangeable, rotating connectors or by employing connector cables in which two leads were crossed. The electrical interconnect system shown in the above-mentioned U.S. Pat. No. 4,134,045 provided a system in which interchangeable connections were provided for successive fixtures in one or the other of the circuits formed by three continuous wire leads. Electrical components constructed in accordance with the above-noted U.S. Pat. No. 4,134,045 are commercially available from the Day-Brite Lighting Division, Emerson Electric Co., Tupelo, Miss. under the trademark ELECTRO/CONNECT.
In general terms, the wiring system disclosed in the above-mentioned U.S. Pat. No. 4,134,045 and commercially available under the trademark ELECTRO/CONNECT system, utilizes four main components. First, a so-called distribution interface which is connected to a panel board by conventional conduit and wire. The distribution interface includes a number of receptacle power circuits to which prewired receptacle power cables may be plugged into. The power cables may lead to branches of lighting fixtures or to wall mounted utility plugs. When it is desired to selectively switch groups or branches of the lighting fixtures independently of others of the lighting fixtures, a so-called switching cable assembly is plugged into a common receptacle provided on each of the lighting fixtures. The switching cable assembly includes a power in receptacle into which an end from one of the flexible power cables is inserted to bring power to that lighting fixture. One or both of the "hot" conductors in the switching cable assembly may be selectively opened and closed by single pole, single throw (SPST) wall mounted switch. Each of the lighting fixtures typically includes a fixture adapter which receives the switched power from the switching cable assembly and into which a flexible jumper cable can be plugged so that the switched power may energize not only the lighting fixture into which the switching cable assembly is plugged, but also may control the energization of a series of lighting fixtures energized by the jumper cable assemblies connected to the fixture adapter of the one fixture. Further, the switching cable assembly includes a power-out receptacle which transfers electrical power through the switching cable assembly in the same manner in which the power was received. Thus, the power may be continued to other branches within the office suite.
Additionally, between the switching cable assembly and the next group of lighting fixtures powered by the circuit, it is necessary to provide either a crossover cable or a so-called rotating coupler in which the pin positions of the "hot" conductors in the plug is reversed or crossed. In this manner, identical switching cable assemblies and remote switches may be utilized thus greatly simplifying the number of components required for this system and greatly simplifying the instructions for installation.
This commercially available ELECTRO/CONNECT plug-in wiring system has met with considerable commercial success because it requires only four standardized, basic components which are prewired and which snaplock together without even the use of simple handtools. Moreover, these components are reuseable so that in the event the floor plan for the office is changed, the same components may be readily unplugged from one circuit and replugged into another circuit as required.
However, as can be appreciated, the number of lighting fixtures that can be powered or energized by one main circuit is limited to the current draw of the lighting fixtures. For example, if power is supplied from a panelboard having 20 amp, 120 volt circuit breakers installed therein, only approximately 15 lighting fixtures may be energized by that circuit if each lighting fixture has four 40 watt fluorescent lamps.
It had been previously recognized that, in commercial buildings, three phase power is often available. By utilizing three phase power to energize the lighting fixtures, it was recognized that the number of distribution interface panels required to energize the lighting fixture could be significantly reduced. However, because of the increased number of conductors available, the complexity of and the number of components required for a three phase, five conductor wiring system was greater than the system illustrated in the above-mentioned U.S. Pat. No. 4,134,045. Thus, there has been a longstanding need for a five conductor, three phase flexible plug-in wiring system which is less complex than prior systems.